From nobody Fri Oct 3 10:13:42 2025 Received: from fra-out-015.esa.eu-central-1.outbound.mail-perimeter.amazon.com (fra-out-015.esa.eu-central-1.outbound.mail-perimeter.amazon.com [18.158.153.154]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 792002DEA7E; Tue, 2 Sep 2025 11:20:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=18.158.153.154 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756812019; cv=none; b=ATyhwFZttGhlqrvm7ij8X9lUxrbOq4QtvDmI+6TezyWjLShqT9lszRSbbMP9yB1MYleNFo08MHIu+cQICDNFGkiFC+kXs1+seREFm5CiEgIKblMN/1nYtz76gQA84cRG+N2Hzfbdf16sMlILUvij1zMbCY0e/ceeG5Fj0vIRgW4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756812019; c=relaxed/simple; bh=ZQ6djA+dRF8qyUysrpr2yHONyU+cbnc0/dSjjBZtaT0=; h=From:To:CC:Subject:Date:Message-ID:References:In-Reply-To: Content-Type:MIME-Version; b=ISrT8awLfHPqmFQsGf0yC/UFuMs7hQf9/FFc9NJfiZ+vlZ31GZUZMmOfZS9CkFTXrRHw0mo4OQFmLTEOWHFUzYRhITBtEoZWEYFDR2xf21PzaZs2569yvGl2YqA7HlKeQ1O7IOWfhwegVGsgskyb0s8W2olCZPbtejER1y44YKw= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amazon.co.uk; spf=pass smtp.mailfrom=amazon.co.uk; dkim=pass (2048-bit key) header.d=amazon.co.uk header.i=@amazon.co.uk header.b=E+nlK09L; arc=none smtp.client-ip=18.158.153.154 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amazon.co.uk Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=amazon.co.uk Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=amazon.co.uk header.i=@amazon.co.uk header.b="E+nlK09L" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.co.uk; i=@amazon.co.uk; q=dns/txt; s=amazoncorp2; t=1756812018; x=1788348018; h=from:to:cc:subject:date:message-id:references: in-reply-to:content-transfer-encoding:mime-version; bh=k50yHNxHR2sgIbO76emzZ9LzG11xHWAXrYW1I23pwro=; b=E+nlK09L3LZSzu0paWxomxfhmW+xs8wPRNMAWl8QLy1Lz5hUoGamt04k qig4SAI98rraQdZIExWts1Pe305uYtnYtv33j5im/dGjRBWm9KFJTJPr2 32tF+NB9/Wg3ExfocIgws6oUT0xbbfKm9YM+8vC2no9APk0FiTGKCoDyp bKDCkzl/adDLK577A/t8gPbx5K2YjaKD50GEAgcKCjPoythEwqLnGb8Ne qDCitFihY+NbbyW/nojiuPk45xS2m8OwBevGITMNTw8NY6Awc9AOoxneC leeB04e7TS/mru4DaRpFMe1TnKMDGrgPJnCWqVMgDhmPEobUyiTVwGsTp A==; X-CSE-ConnectionGUID: JAVDfZM0QRS/seye0FcEGA== X-CSE-MsgGUID: NqQ5f8IeTWu7wbMj5xPXvw== X-IronPort-AV: E=Sophos;i="6.17,290,1747699200"; d="scan'208";a="1403118" Received: from ip-10-6-11-83.eu-central-1.compute.internal (HELO smtpout.naws.eu-central-1.prod.farcaster.email.amazon.dev) ([10.6.11.83]) by internal-fra-out-015.esa.eu-central-1.outbound.mail-perimeter.amazon.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Sep 2025 11:20:04 +0000 Received: from EX19MTAEUC001.ant.amazon.com [54.240.197.225:19714] by smtpin.naws.eu-central-1.prod.farcaster.email.amazon.dev [10.0.43.161:2525] with esmtp (Farcaster) id ecc57207-eff7-433b-8959-d9e5a6fff1f4; Tue, 2 Sep 2025 11:20:04 +0000 (UTC) X-Farcaster-Flow-ID: ecc57207-eff7-433b-8959-d9e5a6fff1f4 Received: from EX19D022EUC003.ant.amazon.com (10.252.51.167) by EX19MTAEUC001.ant.amazon.com (10.252.51.193) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.2562.17; Tue, 2 Sep 2025 11:20:04 +0000 Received: from EX19D022EUC002.ant.amazon.com (10.252.51.137) by EX19D022EUC003.ant.amazon.com (10.252.51.167) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.2562.20; Tue, 2 Sep 2025 11:20:04 +0000 Received: from EX19D022EUC002.ant.amazon.com ([fe80::bd:307b:4d3a:7d80]) by EX19D022EUC002.ant.amazon.com ([fe80::bd:307b:4d3a:7d80%3]) with mapi id 15.02.2562.020; Tue, 2 Sep 2025 11:20:04 +0000 From: "Kalyazin, Nikita" To: "pbonzini@redhat.com" , "shuah@kernel.org" CC: "kvm@vger.kernel.org" , "linux-kselftest@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "michael.day@amd.com" , "david@redhat.com" , "jthoughton@google.com" , "Roy, Patrick" , "Thomson, Jack" , "Manwaring, Derek" , "Cali, Marco" , "Kalyazin, Nikita" Subject: [PATCH v5 1/2] KVM: guest_memfd: add generic population via write Thread-Topic: [PATCH v5 1/2] KVM: guest_memfd: add generic population via write Thread-Index: AQHcG/uHLx3YvTm960eFD//SgYmnaA== Date: Tue, 2 Sep 2025 11:20:03 +0000 Message-ID: <20250902111951.58315-2-kalyazin@amazon.com> References: <20250902111951.58315-1-kalyazin@amazon.com> In-Reply-To: <20250902111951.58315-1-kalyazin@amazon.com> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: Content-Transfer-Encoding: quoted-printable Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" From: Nikita Kalyazin write syscall populates guest_memfd with user-supplied data in a generic way, ie no vendor-specific preparation is performed. This is supposed to be used in non-CoCo setups where guest memory is not hardware-encrypted. The following behaviour is implemented: - only page-aligned count and offset are allowed - if the memory is already allocated, the call will successfully populate it - if the memory is not allocated, the call will both allocate and populate - if the memory is already populated, the call will not repopulate it Signed-off-by: Nikita Kalyazin --- virt/kvm/guest_memfd.c | 64 +++++++++++++++++++++++++++++++++++++++++- 1 file changed, 63 insertions(+), 1 deletion(-) diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index 08a6bc7d25b6..a2e86ec13e4b 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -379,7 +379,9 @@ static int kvm_gmem_mmap(struct file *file, struct vm_a= rea_struct *vma) } =20 static struct file_operations kvm_gmem_fops =3D { - .mmap =3D kvm_gmem_mmap, + .mmap =3D kvm_gmem_mmap, + .llseek =3D default_llseek, + .write_iter =3D generic_perform_write, .open =3D generic_file_open, .release =3D kvm_gmem_release, .fallocate =3D kvm_gmem_fallocate, @@ -390,6 +392,63 @@ void kvm_gmem_init(struct module *module) kvm_gmem_fops.owner =3D module; } =20 +static int kvm_kmem_gmem_write_begin(const struct kiocb *kiocb, + struct address_space *mapping, + loff_t pos, unsigned int len, + struct folio **foliop, + void **fsdata) +{ + struct file *file =3D kiocb->ki_filp; + pgoff_t index =3D pos >> PAGE_SHIFT; + struct folio *folio; + + if (!PAGE_ALIGNED(pos) || len !=3D PAGE_SIZE) + return -EINVAL; + + if (pos + len > i_size_read(file_inode(file))) + return -EINVAL; + + folio =3D kvm_gmem_get_folio(file_inode(file), index); + if (IS_ERR(folio)) + return -EFAULT; + + if (WARN_ON_ONCE(folio_test_large(folio))) { + folio_unlock(folio); + folio_put(folio); + return -EFAULT; + } + + if (folio_test_uptodate(folio)) { + folio_unlock(folio); + folio_put(folio); + return -ENOSPC; + } + + *foliop =3D folio; + return 0; +} + +static int kvm_kmem_gmem_write_end(const struct kiocb *kiocb, + struct address_space *mapping, + loff_t pos, unsigned int len, + unsigned int copied, + struct folio *folio, void *fsdata) +{ + if (copied) { + if (copied < len) { + unsigned int from =3D pos & (PAGE_SIZE - 1); + + folio_zero_range(folio, from + copied, len - copied); + } + kvm_gmem_mark_prepared(folio); + } + + folio_unlock(folio); + folio_put(folio); + + return copied; +} + static int kvm_gmem_migrate_folio(struct address_space *mapping, struct folio *dst, struct folio *src, enum migrate_mode mode) @@ -442,6 +501,8 @@ static void kvm_gmem_free_folio(struct folio *folio) =20 static const struct address_space_operations kvm_gmem_aops =3D { .dirty_folio =3D noop_dirty_folio, + .write_begin =3D kvm_kmem_gmem_write_begin, + .write_end =3D kvm_kmem_gmem_write_end, .migrate_folio =3D kvm_gmem_migrate_folio, .error_remove_folio =3D kvm_gmem_error_folio, #ifdef CONFIG_HAVE_KVM_ARCH_GMEM_INVALIDATE @@ -489,6 +550,7 @@ static int __kvm_gmem_create(struct kvm *kvm, loff_t si= ze, u64 flags) } =20 file->f_flags |=3D O_LARGEFILE; + file->f_mode |=3D FMODE_LSEEK | FMODE_PWRITE; =20 inode =3D file->f_inode; WARN_ON(file->f_mapping !=3D inode->i_mapping); --=20 2.50.1 From nobody Fri Oct 3 10:13:42 2025 Received: from fra-out-003.esa.eu-central-1.outbound.mail-perimeter.amazon.com (fra-out-003.esa.eu-central-1.outbound.mail-perimeter.amazon.com [3.72.182.33]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9FE252F83D0; Tue, 2 Sep 2025 11:20:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=3.72.182.33 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756812029; cv=none; b=Xe0TSPnDL3418oGoDUekeoSkAhXbJs1Zu9AzQjrQAxp9lGsBTgqhXPhaPxGhMxzpJdTM1C6PL4DN7Ndn5k0EIpzt6AaWOuHPnjO8g8A/smjTb5NnfD4aO7gNdogQVKSqGv5cX+IoVOOho1dT0wGBcaDMRWYwLbHQSqb7YUDp+4g= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756812029; c=relaxed/simple; bh=wLPqkcrFWC90MjY5sTrKjuELe2hth0wbMagtCKtQeEM=; h=From:To:CC:Subject:Date:Message-ID:References:In-Reply-To: Content-Type:MIME-Version; b=JJWUxEkBv1H4j3/HX2xakvX+EfGVbC1aoozhdlftwiXeK/A3e4pn3GRp+8aSGByfJr3IEuzG1OWz+WSpnVeBRkr9QtNtbzOGCcykgQ8rvocHfcmiUCWqdTdM1JCqQWi+XV6i+NULKrrZu5CtjfpRde6ifFkHCIuSEYtU0az7Md8= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amazon.co.uk; spf=pass smtp.mailfrom=amazon.co.uk; dkim=pass (2048-bit key) header.d=amazon.co.uk header.i=@amazon.co.uk header.b=lsFmIzzh; arc=none smtp.client-ip=3.72.182.33 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amazon.co.uk Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=amazon.co.uk Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=amazon.co.uk header.i=@amazon.co.uk header.b="lsFmIzzh" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.co.uk; i=@amazon.co.uk; q=dns/txt; s=amazoncorp2; t=1756812027; x=1788348027; h=from:to:cc:subject:date:message-id:references: in-reply-to:content-transfer-encoding:mime-version; bh=4U/GLmw/FZs2LtG2FoqidgM1jKHBj0dCkKYDbjnXvsY=; b=lsFmIzzhuWwEkaeVhlhqS7kh3HWWO5wh6OqLoAePCCfAC3CaTF4uBRX7 rEOPLR4X3zKiWGXXE31SVX/smaopj4/PmvfBgA/LGu1GDZolU5ajZKXDG eefi88HT2AmUMVoX1uAMoCpz1nBwPI6KXB+HKoB0c3Kl+ej4uXguQyuCI gQE5XslA6RPZgqYvnBqPwu+8ABN4KH8flVOUaFOCjOeEAMAJhNAG/dCx4 1gQXfZ2LV7NmjQgD3lbxdTKo5CmTbpyZnnfsA8XPrwlgOt0HhC7U7O8ft 0W02WCzookzNn3zgbZAf8wLsuJfs5sRXTWVC5JuXL/60t+r/BbBEn4/NN g==; X-CSE-ConnectionGUID: RPbfGhQvT7SDDE89GnEZoQ== X-CSE-MsgGUID: ix4JFTmkRaGaeMwIGDEllw== X-IronPort-AV: E=Sophos;i="6.18,214,1751241600"; d="scan'208";a="1511844" Received: from ip-10-6-11-83.eu-central-1.compute.internal (HELO smtpout.naws.eu-central-1.prod.farcaster.email.amazon.dev) ([10.6.11.83]) by internal-fra-out-003.esa.eu-central-1.outbound.mail-perimeter.amazon.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Sep 2025 11:20:16 +0000 Received: from EX19MTAEUB002.ant.amazon.com [54.240.197.224:28163] by smtpin.naws.eu-central-1.prod.farcaster.email.amazon.dev [10.0.43.161:2525] with esmtp (Farcaster) id 0dc98258-151a-46cc-81b3-dce1ed47247b; Tue, 2 Sep 2025 11:20:16 +0000 (UTC) X-Farcaster-Flow-ID: 0dc98258-151a-46cc-81b3-dce1ed47247b Received: from EX19D022EUC002.ant.amazon.com (10.252.51.137) by EX19MTAEUB002.ant.amazon.com (10.252.51.59) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.2562.17; Tue, 2 Sep 2025 11:20:16 +0000 Received: from EX19D022EUC002.ant.amazon.com (10.252.51.137) by EX19D022EUC002.ant.amazon.com (10.252.51.137) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.2562.20; Tue, 2 Sep 2025 11:20:15 +0000 Received: from EX19D022EUC002.ant.amazon.com ([fe80::bd:307b:4d3a:7d80]) by EX19D022EUC002.ant.amazon.com ([fe80::bd:307b:4d3a:7d80%3]) with mapi id 15.02.2562.020; Tue, 2 Sep 2025 11:20:15 +0000 From: "Kalyazin, Nikita" To: "pbonzini@redhat.com" , "shuah@kernel.org" CC: "kvm@vger.kernel.org" , "linux-kselftest@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "michael.day@amd.com" , "david@redhat.com" , "jthoughton@google.com" , "Roy, Patrick" , "Thomson, Jack" , "Manwaring, Derek" , "Cali, Marco" , "Kalyazin, Nikita" Subject: [PATCH v5 2/2] KVM: selftests: update guest_memfd write tests Thread-Topic: [PATCH v5 2/2] KVM: selftests: update guest_memfd write tests Thread-Index: AQHcG/uOPOuTx3pVLkmJVq9l2Ktv1Q== Date: Tue, 2 Sep 2025 11:20:15 +0000 Message-ID: <20250902111951.58315-3-kalyazin@amazon.com> References: <20250902111951.58315-1-kalyazin@amazon.com> In-Reply-To: <20250902111951.58315-1-kalyazin@amazon.com> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: Content-Transfer-Encoding: quoted-printable Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" From: Nikita Kalyazin This is to reflect that the write syscall is now implemented for guest_memfd. Signed-off-by: Nikita Kalyazin --- .../testing/selftests/kvm/guest_memfd_test.c | 86 +++++++++++++++++-- 1 file changed, 80 insertions(+), 6 deletions(-) diff --git a/tools/testing/selftests/kvm/guest_memfd_test.c b/tools/testing= /selftests/kvm/guest_memfd_test.c index b3ca6737f304..1236e31f5041 100644 --- a/tools/testing/selftests/kvm/guest_memfd_test.c +++ b/tools/testing/selftests/kvm/guest_memfd_test.c @@ -24,18 +24,91 @@ #include "test_util.h" #include "ucall_common.h" =20 -static void test_file_read_write(int fd) +static void test_file_read(int fd) { char buf[64]; =20 TEST_ASSERT(read(fd, buf, sizeof(buf)) < 0, "read on a guest_mem fd should fail"); - TEST_ASSERT(write(fd, buf, sizeof(buf)) < 0, - "write on a guest_mem fd should fail"); TEST_ASSERT(pread(fd, buf, sizeof(buf), 0) < 0, "pread on a guest_mem fd should fail"); - TEST_ASSERT(pwrite(fd, buf, sizeof(buf), 0) < 0, - "pwrite on a guest_mem fd should fail"); +} + +static void test_file_write(int fd, size_t total_size) +{ + size_t page_size =3D getpagesize(); + void *buf =3D NULL; + int ret; + + ret =3D posix_memalign(&buf, page_size, total_size); + TEST_ASSERT_EQ(ret, 0); + + /* Check arguments correctness checks work as expected */ + + ret =3D pwrite(fd, buf, page_size - 1, 0); + TEST_ASSERT(ret =3D=3D -1, "write unaligned count on a guest_mem fd shoul= d fail"); + TEST_ASSERT_EQ(errno, EINVAL); + + ret =3D pwrite(fd, buf, page_size, 1); + TEST_ASSERT(ret =3D=3D -1, "write unaligned offset on a guest_mem fd shou= ld fail"); + TEST_ASSERT_EQ(errno, EINVAL); + + ret =3D pwrite(fd, buf, page_size, total_size); + TEST_ASSERT(ret =3D=3D -1, "writing past the file size on a guest_mem fd = should fail"); + TEST_ASSERT_EQ(errno, EINVAL); + + ret =3D pwrite(fd, NULL, page_size, 0); + TEST_ASSERT(ret =3D=3D -1, "supplying a NULL buffer when writing a guest_= mem fd should fail"); + TEST_ASSERT_EQ(errno, EFAULT); + + /* Check double population is not allowed */ + + ret =3D pwrite(fd, buf, page_size, 0); + TEST_ASSERT(ret =3D=3D page_size, "page-aligned write on a guest_mem fd s= hould succeed"); + + ret =3D pwrite(fd, buf, page_size, 0); + TEST_ASSERT(ret =3D=3D -1, "write on already populated guest_mem fd shoul= d fail"); + TEST_ASSERT_EQ(errno, ENOSPC); + + ret =3D fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE, 0, page= _size); + TEST_ASSERT(!ret, "fallocate(PUNCH_HOLE) should succeed"); + + /* Check population is allowed again after punching a hole */ + + ret =3D pwrite(fd, buf, page_size, 0); + TEST_ASSERT(ret =3D=3D page_size, + "page-aligned write on a punched guest_mem fd should succeed"); + + ret =3D fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE, 0, page= _size); + TEST_ASSERT(!ret, "fallocate(PUNCH_HOLE) should succeed"); + + /* Check population of already allocated memory is allowed */ + + ret =3D fallocate(fd, FALLOC_FL_KEEP_SIZE, 0, page_size); + TEST_ASSERT(!ret, "fallocate with aligned offset and size should succeed"= ); + + ret =3D pwrite(fd, buf, page_size, 0); + TEST_ASSERT(ret =3D=3D page_size, "write on a preallocated guest_mem fd s= hould succeed"); + + ret =3D fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE, 0, page= _size); + TEST_ASSERT(!ret, "fallocate(PUNCH_HOLE) should succeed"); + + /* Check population works until an already populated page is encountered = */ + + ret =3D pwrite(fd, buf, total_size, 0); + TEST_ASSERT(ret =3D=3D total_size, "page-aligned write on a guest_mem fd = should succeed"); + + ret =3D fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE, 0, page= _size); + TEST_ASSERT(!ret, "fallocate(PUNCH_HOLE) should succeed"); + + ret =3D pwrite(fd, buf, total_size, 0); + TEST_ASSERT(ret =3D=3D page_size, "write on a guest_mem fd should not ove= rwrite data"); + + ret =3D fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE, 0, tota= l_size); + TEST_ASSERT(!ret, "fallocate(PUNCH_HOLE) should succeed"); + + + free(buf); } =20 static void test_mmap_supported(int fd, size_t page_size, size_t total_siz= e) @@ -281,7 +354,8 @@ static void test_guest_memfd(unsigned long vm_type) =20 fd =3D vm_create_guest_memfd(vm, total_size, flags); =20 - test_file_read_write(fd); + test_file_read(fd); + test_file_write(fd, total_size); =20 if (flags & GUEST_MEMFD_FLAG_MMAP) { test_mmap_supported(fd, page_size, total_size); --=20 2.50.1